Methods of programming memory

ABSTRACT

Methods of programming a memory include applying a programming voltage on an access line selected for a programming operation of a single page of the memory, applying a second voltage on an access line unselected for the programming operation, increasing the programming voltage for a first plurality of steps of the programming operation, and increasing the second voltage for a second plurality of steps of a first portion of the programming operation, then decreasing the second voltage at a particular point of the programming operation after completing the second plurality of steps and before completing the first plurality of steps.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/248,130, filed Aug. 26, 2016 (allowed), which is a divisional ofapplication Ser. No. 14/633,287, filed Feb. 27, 2015 and issued as U.S.Pat. No. 9,455,042 on Sep. 27, 2016, which is a continuation of U.S.application Ser. No. 12/702,948, filed Feb. 9, 2010 and issued as U.S.Pat. No. 8,982,631 on Mar. 17, 2015, which applications are commonlyassigned and incorporated entirely herein by reference.

FIELD

The present disclosure relates generally to memory devices and inparticular the present disclosure relates to memory devices and methodsof programming memories.

BACKGROUND

Memory devices are typically provided as internal, semiconductor,integrated circuits in computers or other electronic devices. There aremany different types of memory including random-access memory (RAM),read only memory (ROM), dynamic random access memory (DRAM), synchronousdynamic random access memory (SDRAM), and flash memory.

Flash memory devices have developed into a popular source ofnon-volatile memory for a wide range of electronic applications. Flashmemory devices typically use a one-transistor memory cell that allowsfor high memory densities, high reliability, and low power consumption.Changes in threshold voltage of the cells, through programming of acharge storage node (e.g., a floating gate or charge trap), or otherphysical phenomena (e.g., phase change or polarization), determine thedata state of each cell. Common uses for flash memory include personalcomputers, personal digital assistants (PDAs), digital cameras, digitalmedia players, digital recorders, games, appliances, vehicles, wirelessdevices, cellular telephones, and removable memory modules, and the usesfor flash memory continue to expand.

Flash memory typically utilizes one of two basic architectures known asNOR flash and NAND flash. The designation is derived from the logic usedto read the devices. In NOR flash architecture, a logical column ofmemory cells is coupled in parallel with each memory cell coupled to adata line, such as those typically referred to as bit lines. In NANDflash architecture, a column of memory cells is coupled in series withonly the first memory cell of the column coupled to a bit line.

As the performance and complexity of electronic systems increase, therequirement for additional memory in a system also increases. However,in order to continue to reduce the costs of the system, the parts countmust be kept to a minimum. This can be accomplished by increasing thememory density of an integrated circuit by using such technologies asmultilevel cells (MLC). For example, MLC NAND flash memory is a verycost effective non-volatile memory.

Multilevel cells can take advantage of the analog nature of atraditional flash cell by assigning a data value, e.g., a bit pattern,to a specific threshold voltage (Vt) range stored on the cell. Thistechnology permits the storage of two or more bits of information percell, depending on the quantity of voltage ranges assigned to the celland the stability of the assigned voltage ranges during the lifetimeoperation of the memory cell.

For example, a cell may be assigned four different threshold voltageranges of 200 mV for each range. Typically, a margin, e.g., a deadspace, of 0.2V to 0.4V is between each range to keep the ranges fromoverlapping. For example, if the threshold voltage of the cell is withinthe first range, the cell may be assigned a data value having a logical11 state and is typically considered the erased state of the cell. Ifthe threshold voltage is within the second range, the cell may beassigned a data value having a logical 01 state. This may continue foras many ranges that are used for the cell provided these thresholdvoltage (Vt) ranges remain stable during the lifetime operation of thememory cell.

Since two or more data values may be assigned to each MLC, the width ofeach of the threshold voltage ranges for each data value can be veryimportant. The width is related to many variables in the operation of amemory circuit. For example, a cell could be verified at one temperatureand read at a different temperature. The circuitry that determines ifthe cell is erased or programmed to a Vt level within the correct Vtrange has to make that determination. That circuitry has some of itscharacteristics influenced by temperature. A Vt range generally takesinto account all of these types of differences to accommodate a shift inthe perceived threshold voltage of a memory cell under differentoperating conditions. In order for the memory cell to operateeffectively, the width of the Vt ranges corresponding to the variousdata values that can be assigned to the memory cell, plus a marginbetween each Vt range, should amount to the available range of thresholdvoltages of the memory cell.

Programming in a memory typically is accomplished using a plurality ofprogramming pulses that increase in voltage as programming occurs, witheach programming pulse followed by verification to determine whethercells that are being programmed have been programmed to their desiredthreshold voltages. This is because some cells program at differentvoltages than other cells. For cells that are not being programmed butare coupled to the same bit line as a cell being programmed, a set ofinhibit pulses is applied to their word lines to, for example, reducecoupling effects and over-programming. The inhibit pulses traditionallyincrease in voltage as programming occurs as well.

In a memory in which the pattern of cells and lines in the memory issuch that at low program voltages most of the memory cells on bit linesthat are inhibited are adjacent to other memory cells on bit lines thatare being programmed, typical errors are more associated with thoseregions of low program voltages rather than high program voltages asmemory cells scale down. This is due in part to the disturb due toincreasing Vchannel loss between the pattern where inhibited bit lineshave adjacent bit lines connected to memory cells that are beingprogrammed, and the pattern where inhibited bit lines have adjacent bitlines connected to memory cells that are also inhibited fromprogramming.

For reasons such as those stated above, and for other reasons, such asthose stated below, which will become apparent to those skilled in theart upon reading and understanding the present specification, there is aneed in the art for, among other things, reducing disturbance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart diagram of a method according to an embodiment ofthe present disclosure;

FIG. 1A is a graph showing a traditional programming sequence for amemory;

FIG. 2 is a graph showing one programming embodiment for the embodimentof FIG. 1;

FIG. 3 is a graph showing another programming embodiment for theembodiment of FIG. 1;

FIG. 4A is a diagram of a self-boost boosting scheme;

FIG. 4B is a diagram of an AMDSSB boosting scheme;

FIG. 4C is a diagram of a local self-boosting scheme; and

FIG. 5 is a functional block diagram of a system according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description of the embodiments, reference ismade to the accompanying drawings that form a part hereof. In thedrawings, like numerals describe substantially similar componentsthroughout the several views. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention. Other embodiments may be utilized and structural, logical,and electrical changes may be made without departing from the scope ofthe present invention.

The following detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present disclosure is defined onlyby the appended claims, along with the full scope of equivalents towhich such claims are entitled.

In various embodiments of the present invention, a channel voltage isboosted for a first portion (e.g., number) of programming pulses of aplurality of programming pulses for the memory. Channel voltage isdependent upon the waveform of the inhibit voltage, and the programmingscheme used for the memory. When a criteria is met, such as a number ofprogramming pulses, a determined threshold voltage of the cell beingprogrammed, a completion of a determined portion of the programming orcompletion of programming of a certain program level, or the like, thechannel voltage is boosted differently for a second portion of theprogramming sequence.

Various embodiments for boosting the channel voltage at the transitionbetween the first and second portion of programming pulses include forexample using a different boosting scheme for the first portion, orusing a different inhibit voltage waveform for the first portion. Suchembodiments can provide an improved programming operation in the lowprogram voltage region of a programming sequence to reduce disturb inthose regions of the memory where a CS2 pattern is dominant (i.e., apattern where both bit lines adjacent to an inhibited bit line are notbeing inhibited from programming). Once a criteria is met, such as adetermined threshold voltage reached by the cells being programmed, acertain number of program pulses, or the like, the channel voltage isboosted differently.

Embodiments of the present invention provide various boosting schemesto, for example, reduce program disturb in regions of a memory where amajority of bit lines being inhibited are adjacent to bit lines that arebeing programmed on both sides. NAND memory is programmed on a pagebasis. Therefore, a programming bit line is not immediately adjacent toanother programming bit line. Traditional programming schemes areconfigured to reduce disturb issues in a high program voltage regionwhere the dominant pattern is one in which the bit line being inhibitedis sandwiched by bit lines that are also inhibited (also referred to asa CS0 pattern). However, as NAND continues to scale downward, memoryregions in which the dominant pattern has both bit lines adjacent to thebit line being inhibited are being programmed and are therefore notinhibited (also referred to as a CS2 pattern) are increasingly common,and the raw bit error rates that begin to dominate among total errors inthe memory are those associated with that CS2 pattern, since the channelboost voltage (also referred to as Vchannel) loss between the CS2pattern and the CS0 pattern increases.

Channel boosting schemes can include, for example, boosting the inhibitvoltages applied to certain access lines (which are typically referredto as word lines) during a low program voltage portion of a programmingsequence, or boosting the channel voltage applied to word lines using adifferent boosting scheme during a low program voltage portion of aprogramming sequence.

In one embodiment, a method 100 of programming a memory is shown inFIG. 1. Method 100 comprises boosting a channel voltage to a channel ofthe memory for a first portion of a plurality of programming pulses of aprogramming sequence in block 102 and, when a criteria is met, boostingthe channel voltage differently for a second portion of the plurality ofprogramming pulses of the programming sequence in block 104. Boostingdifferently in one embodiment comprises boosting inhibited memory cellsto a higher voltage during the first portion of the programming than thesecond portion of the programming. In one embodiment, the higher voltageto which the inhibited memory cells are boosted is higher than atraditional inhibit pulse voltage for the first portion of programming,and the different boosting for the second portion of programming is atraditional inhibit voltage waveform.

In one embodiment, boosting the channel voltage is accomplished byapplying a different inhibit voltage waveform to non-programming cellsof a column, as is shown in FIG. 2. For example, during application of aset of inhibit pulses, a voltage of that set of inhibit pulses isboosted during a low program voltage portion of the programmingsequence, when the dominant pattern is expected to be the CS2 pattern.That is, the set of inhibit pulses are in one embodiment boosted involtage for the first portion of the programming sequence to compensatefor disturb when a predominant pattern is expected to be one where bothof the bit lines adjacent to an inhibited bit line are not inhibited(i.e., the cells coupled to those bit lines are still programming). Whena criteria is met, for example the criteria discussed herein, theinhibit voltage waveform is shifted back and the inhibit pulses areapplied as in a traditional programming operation. This is in oneembodiment done when the CS0 pattern is expected to dominate the array.

A graph 150 showing traditional programming of a memory is shown in FIG.1A. As can be seen in FIG. 1A, a programming sequence comprising aplurality of programming pulses 152 steps up from a low program voltageto a higher program voltage as the pulse number increases. The programscheme used may be a self-boost or advanced modified drain side selfboost (AMDSSB). The inhibit voltage waveform 154 also steps up from alow inhibit voltage to a higher inhibit voltage as the pulse numberincreases. The channel boosting voltage 158 jumps in a region,designated as the CS0region, that is, a high program voltage regionwhere the dominant pattern is one in which the bit line being inhibitedis sandwiched by bit lines that are also inhibited. Therefore, thedifference 160 between the program voltage and the channel voltage ishigher in the CS0 region.

A graph 200 showing the programming of the embodiment described in FIG.1 using a different inhibit voltage waveform is shown in FIG. 2. As canbe seen in FIG. 2, a programming sequence comprising a plurality ofprogramming pulses 202 steps up from a low program voltage to a higherprogram voltage as the pulse number increases. In a region, designatedas the CS2 region, when a pattern of both bit lines adjacent to aninhibited bit line not being inhibited is expected to dominate, a set ofboosted inhibit pulses 204 is applied to a subset of word lines near theword line being programmed, such as in a scheme as described below. Thisset of inhibit pulses shown at 205 starts at a higher voltage than thevoltage of traditional inhibit pulses as described above, to compensatefor Vchannel loss in the regions of the memory where the CS2 pattern isdominant.

The resultant channel voltage is shown at 208. During that portion ofthe programming sequence when a CS2 pattern is likely dominant, thechannel voltage is higher than a traditional channel voltage. Thischannel voltage, boosted by a higher inhibit voltage, can reduce disturbduring that portion of the programming sequence. Traditional programminghas the channel voltage lower than that of the present embodiments whena CS2 pattern is likely dominant in the memory, and about the same asthat of the present embodiments when a CS0 pattern is likely dominant inthe memory, meaning that traditional programming is optimized to reducedisturb errors when a CS0pattern is likely dominant in the memory. Incontrast, one or more of the embodiments of the present disclosure, forexample, is configured to further reduce disturb errors when either theCS2 or the CS0 patterns are dominant in the memory.

When a determined criteria is met, as indicated by dashed line 206, theinhibit voltage waveform is shifted back and programming continues witha traditional set of inhibit pulses, leading to a traditional channelvoltage. The criteria can be chosen from a number of conditions. Thesatisfaction of the chosen condition triggers the shifting of theinhibit voltage pulses. Examples of criteria include, but are notlimited to, the CS2 pattern dominance moves to CS0 pattern dominance,completion of level 1 programming, that is programming to produce afirst shift in data value in the cell, reaching a determined thresholdvoltage for the cells being programmed, reaching a determined number ofprogram pulses, or the like. The difference 210 between the programvoltage and the channel voltage remains substantially constant.

In operation, the embodiment shown in FIG. 2 operates as follows. Amethod of programming a memory includes applying a programming voltageon a selected word line, and applying an inhibit voltage on unselectedword lines. For programming a single page of the memory, the programmingvoltage is incremented up in a plurality of steps, and the inhibitvoltage shifts down at a first point of the single page programming, andthen is incremented up after the first point. The first point may bedetermined by a number of programming cycles having been reached.

In another embodiment, a different boosting scheme is used for a firstportion of the plurality of programming pulses, boosting the channelvoltage with this different program scheme. A graph 300 showing theprogramming of an embodiment described in FIG. 1 using differentboosting schemes to boost the channel is shown in FIG. 3. As can be seenin FIG. 3, a programming sequence comprising a plurality of programmingpulses 302 steps up from a low program voltage to a higher programvoltage as the pulse number increases. A set of inhibit pulses 304 alsosteps up from a low inhibit voltage to a higher inhibit pulse voltage asthe pulse number increases. In a region 309, designated as the CS2region, when a pattern of both bit lines adjacent to an inhibited bitline are not being inhibited is expected to dominate, the channelvoltage, which is traditionally lower when the memory is dominated by aCS2 pattern, is boosted to a higher voltage than a traditional channelvoltage by using a different boosting scheme. This boosting of channelvoltage when the memory is likely to be dominated by a CS2 pattern isdone, for example, to compensate for Vchannel loss in that region of thememory when the CS2 pattern is dominant. The channel voltage Vchannel isshown at 308, and indicates a channel voltage that is higher thantraditional channel voltages for programming in the CS2 region. Thisboosted voltage can reduce disturb in that region of the memory duringthat portion of the programming sequence. Boosting of the channelvoltage is accomplished in various embodiments as described below.

As was the case in the first embodiment, when a determined criteria ismet, as indicated by dashed line 306, the channel voltage is boosteddifferently. The criteria can be chosen from a number of conditions. Thesatisfaction of the chosen condition triggers the boosting schemechange. Examples of criteria include, but are not limited to, the CS2pattern dominance moves to CS0 pattern dominance, completion of level 1programming, that is programming to level 1, reaching a determinedthreshold voltage for the cells being programmed, reaching a determinednumber of program pulses, or the like. The difference 310 between theprogram voltage and the channel voltage remains substantially constant.

In operation, the embodiment shown in FIG. 3 operates as follows. Amethod of programming a memory according to the embodiment of FIG. 3includes applying a programming voltage on a selected word line,applying an inhibit voltage on unselected word lines, and applying anisolation voltage on the unselected word lines. A different boostingscheme is applied before a first point in the programming and after thefirst point in the programming. The first point may be determined by anumber of programming cycles having been reached.

Embodiments of various boosting schemes are shown in FIGS. 4A, 4B, and4C. The boosting schemes of FIGS. 4A and 4B are used traditionally inprogramming memories. For example, as shown in FIG. 4A, a conventionalself-boost scheme boosts all (typically 64) word lines which boosts thechannel voltage. Self-boost is typically configured to more efficientlyprogram during portions when the CS0 pattern dominates.

FIG. 4B shows an advanced modified drain side self boost (AMDSSB)boosting scheme. Such a scheme may be used for programming in the CS0region in the embodiments shown and described, for example, in FIGS. 2and 3. AMDSSB only boosts voltage to the channels corresponding to wordlines near a word line being programmed as well as all channelscorresponding to word lines between the programming word line and adrain side select gate, typically many more word lines than in a localself boosting scheme as described below. AMDSSB boosting is described ingreater detail in U.S. Published Patent Application 20080225589,commonly owned by the owner of the present application.

FIG. 4C shows a local self-boosting scheme. Such a scheme may be usedfor programming in the CS2 region, prior to the criteria being met, inembodiments such as that shown and described, for example, in FIG. 3.This scheme boosts only a portion of the channels in a column byboosting typically on the order of about five to seven word lines,including the channel corresponding to the word line being programmedand the channels of approximately two to three adjacent word lines oneach side of the word line being programmed. Further, in a local selfboosting scheme, word lines adjacent the word lines used for the localself boost may be grounded.

While a channel voltage is shown herein as being boosted before thecriteria is met, it should be understood that channel voltages areaffected by inhibit voltage waveforms and programming schemes, and achannel voltage could be developed that is boosted higher than atraditional channel voltage and then shifted back after the criteria ismet without departing from the scope of the disclosure.

FIG. 5 is a simplified block diagram of a memory device 501 according toan embodiment of the disclosure, and on which various embodiments of thedisclosure can be practiced. Memory device 501 includes an array ofmemory cells 504 arranged in rows and columns. In general, however, theembodiments described herein are adaptable to any array architecturepermitting generation of a data signal indicative of the thresholdvoltage of each memory cell.

A row decode circuitry 508 and a column decode circuitry 510 areprovided to decode address signals provided to the memory device 501.Address signals are received and decoded to access memory array 504.Memory device 501 also includes input/output (I/O) control circuitry 512to manage input of commands, addresses and data to the memory device 501as well as output of data and status information from the memory device501. An address register 514 is coupled between I/O control circuitry512 and row decode circuitry 508 and column decode circuitry 510 tolatch the address signals prior to decoding. A command register 524 iscoupled between I/O control circuitry 512 and control logic 516 to latchincoming commands. Control logic 516 controls access to the memory array504 in response to the commands and generates status information for theexternal processor 530. The control logic 516 is coupled to row decodecircuitry 508 and column decode circuitry 510 to control the row decodecircuitry 508 and column decode circuitry 510 in response to theaddresses.

Control logic 516 can be coupled to a sample and hold circuitry 518. Thesample and hold circuitry 518 latches data, either incoming or outgoing,in the form of analog data signals. For example, the sample and holdcircuitry could contain capacitors or other analog storage devices forsampling either an incoming data signal representing data to be writtento a memory cell or an outgoing data signal indicative of the thresholdvoltage sensed from a memory cell. The sample and hold circuitry 518 mayfurther provide for amplification and/or buffering of the sampled datato provide a stronger data signal to an external device.

The handling of analog data signals may take an approach similar to anapproach well known in the area of CMOS imager technology, where chargelevels generated at pixels of the imager in response to incidentillumination are stored on capacitors. These charge levels are thenconverted to signals using a differential amplifier with a referencecapacitor as a second input to the differential amplifier. The output ofthe differential amplifier is then passed to analog-to-digitalconversion (ADC) devices to obtain a digital value representative of anintensity of the illumination. In the present embodiments, a charge maybe stored on a capacitor in response to subjecting it to a data signalindicative of an actual or target threshold voltage of a memory cell forreading or programming, respectively, the memory cell. This charge couldthen be converted to an analog data signal using a differentialamplifier having a grounded input or other reference signal as a secondinput. The output of the differential amplifier could then be passed tothe I/O control circuitry 512 for output from the memory device, in thecase of a read operation, or used for comparison during one or moreverify operations in programming the memory device. It is noted that theI/O control circuitry 512 could optionally include analog-to-digitalconversion functionality and digital-to-analog conversion (DAC)functionality to convert read data from an analog data signal to adigital bit pattern and to convert write data from a digital bit patternto an analog signal such that the memory device 501 could be adapted forcommunication with either an analog or digital data interface.

During a write operation, target memory cells of the memory array 504are programmed until voltages indicative of their Vt levels match thelevels held in the sample and hold circuitry 518. This can beaccomplished, as one example, using differential sensing devices tocompare the held voltage level to a threshold voltage of the targetmemory cell. Much like traditional memory programming, programmingpulses could be applied to a target memory cell to increase itsthreshold voltage until reaching or exceeding the desired value. In aread operation, the Vt levels of the target memory cells are passed tothe sample and hold circuitry 518 for transfer to an external processor(not shown in FIG. 5) either directly as analog signals or as digitizedrepresentations of the analog signals depending upon whether ADC/DACfunctionality is provided external to, or within, the memory device.

Threshold voltages of cells may be determined in a variety of manners.For example, a word line voltage could be sampled at the point when thetarget memory cell becomes activated. Alternatively, a boosted voltagecould be applied to a first source/drain side of a target memory cell,and the threshold voltage could be taken as a difference between itscontrol gate voltage and the voltage at its other source/drain side. Bycoupling the voltage to a capacitor, charge would be shared with thecapacitor to store the sampled voltage. Note that the sampled voltageneed not be equal to the threshold voltage, but merely indicative ofthat voltage. For example, in the case of applying a boosted voltage toa first source/drain side of the memory cell and a known voltage to itscontrol gate, the voltage developed at the second source/drain side ofthe memory cell could be taken as the data signal as the developedvoltage is indicative of the threshold voltage of the memory cell.

Sample and hold circuitry 518 may include caching, i.e., multiplestorage locations for each data value, such that the memory device 501may be reading a next data value while passing a first data value to theexternal processor, or receiving a next data value while writing a firstdata value to the memory array 504. A status register 522 is coupledbetween I/O control circuitry 512 and control logic 516 to latch thestatus information for output to the external processor.

Memory device 501 receives control signals at control logic 516 over acontrol link 532. The control signals may include a chip enable CE#, acommand latch enable CLE, an address latch enable ALE, and a writeenable WE#. Memory device 501 may receive commands (in the form ofcommand signals), addresses (in the form of address signals), and data(in the form of data signals) from an external processor over amultiplexed input/output (I/O) bus 534 and output data to the externalprocessor over I/O bus 534.

In a specific example, commands are received over input/output (I/O)pins [7:0] of I/O bus 534 at I/O control circuitry 512 and are writteninto command register 524. The addresses are received over input/output(I/O) pins [7:0] of bus 534 at I/O control circuitry 512 and are writteninto address register 514. The data may be received over input/output(I/O) pins [7:0] for a device capable of receiving eight parallelsignals, or input/output (I/O) pins [15:0] for a device capable ofreceiving sixteen parallel signals, at I/O control circuitry 512 and aretransferred to sample and hold circuitry 518. Data also may be outputover input/output (I/O) pins [7:0] for a device capable of transmittingeight parallel signals or input/output (I/O) pins [15:0] for a devicecapable of transmitting sixteen parallel signals. It will be appreciatedby those skilled in the art that additional circuitry and signals can beprovided, and that the memory device of FIG. 5 has been simplified tohelp focus on the embodiments of the disclosure. Additionally, while thememory device of FIG. 5 has been described in accordance with popularconventions for receipt and output of the various signals, it is notedthat the various embodiments are not limited by the specific signals andI/O configurations described. For example, command and address signalscould be received at inputs separate from those receiving the datasignals, or data signals could be transmitted serially over a single I/Oline of I/O bus 534. Because the data signals represent bit patternsinstead of individual bits, serial communication of an 8-bit data signalcould be as efficient as parallel communication of eight signalsrepresenting individual bits.

A program function on selected cells, blocks, pages, or the like of thememory 400 is performed as described above with respect to FIGS. 1-3.

Programming methods and memories using those programming methods havebeen shown that include boosting a channel voltage when a CS2 pattern isexpected to be dominant (i.e., a pattern where both bit lines adjacentto an inhibited bit line are not inhibited), such as to reduce disturberrors when such a patterns is dominant.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement, which is calculated to achieve the same purpose,may be substituted for the specific embodiment shown. This applicationis intended to cover any adaptations or variations of the presentinvention. Therefore, it is manifestly intended that this invention belimited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method of programming a memory, comprising:applying a programming voltage on an access line selected for aprogramming operation of a single page of the memory; applying a secondvoltage on an access line unselected for the programming operation;increasing the programming voltage for a first plurality of steps of theprogramming operation; and increasing the second voltage for a secondplurality of steps of a first portion of the programming operation, thendecreasing the second voltage at a particular point of the programmingoperation after completing the second plurality of steps and beforecompleting the first plurality of steps.
 2. The method of claim 1,further comprising returning to increasing the second voltage during asecond portion of the programming operation.
 3. The method of claim 2,wherein returning to increasing the second voltage comprises returningto increasing the second voltage for a third plurality of steps of theprogramming operation.
 4. The method of claim 1, wherein the particularpoint is determined by a number of programming cycles having beenreached.
 5. The method of claim 1, wherein the particular point isdetermined by completion of programming for a certain programming level.6. The method of claim 1, wherein the particular point is determined bya shift in pattern of a plurality of bit lines coupled to memory cellsof the access line selected for programming from a first pattern, whereboth bit lines adjacent to a bit line inhibited from programming are notbeing inhibited from programming, being dominant, to a second pattern,where both bit lines adjacent to a bit line inhibited from programmingare being inhibited from programming, being dominant.
 7. The method ofclaim 1, wherein the particular point is determined by reaching adetermined threshold voltage for memory cells of the selected accessline being programmed.
 8. The method of claim 1, wherein the particularpoint is determined by reaching a particular number of steps of thefirst plurality of steps.
 9. A method of programming a memory,comprising: applying a programming voltage on an access line selectedfor a programming operation of a single page of the memory; applying asecond voltage on an access line unselected for the programmingoperation; developing a boosted channel voltage while applying theprogramming voltage and applying the second voltage, wherein theprogramming voltage is expected to increase a threshold voltage of amemory cell of the selected access line having the boosted channelvoltage, and wherein the second voltage is expected to inhibit anincrease of a threshold voltage of a memory cell of the unselectedaccess line having the boosted channel voltage; increasing theprogramming voltage for a first plurality of steps of the programmingoperation; and increasing the second voltage for a second plurality ofsteps during a first portion of the programming operation, thendecreasing the second voltage at a particular point of the programmingoperation after completing the second plurality of steps and beforecompleting the first plurality of steps.
 10. The method of claim 9,wherein developing the boosted channel voltage comprises developing theboosted channel voltage for the memory cell of the selected access lineand for memory cells of a plurality of access lines unselected for theprogramming operation.
 11. The method of claim 10, wherein developingthe boosted channel voltage for the memory cell of the selected accessline and for the memory cells of the plurality of access linesunselected for the programming operation comprises developing theboosted channel voltage for each memory cell connected in series withthe memory cell of the selected access line.
 12. The method of claim 11,wherein developing the boosted channel voltage for the memory cell ofthe selected access line and for the memory cells of the plurality ofaccess lines unselected for the programming operation further comprisesdeveloping the boosted channel voltage for each memory cell connected inseries with the memory cell of the selected access line prior to theparticular point of the programming operation, and developing theboosted channel voltage for less than all memory cells connected inseries with the memory cell of the selected access line after theparticular point of the programming operation.
 13. The method of claim10, wherein developing the boosted channel voltage for the memory cellof the selected access line and for the memory cells of the plurality ofaccess lines unselected for the programming operation comprisesdeveloping the boosted channel voltage for less than all memory cellsconnected in series with the memory cell of the selected access line.14. The method of claim 9, further comprising returning to increasingthe second voltage during a second portion of the programming operation.15. The method of claim 14, wherein returning to increasing the secondvoltage during the second portion of the programming operation comprisesreturning to increasing the second voltage during the second portion ofthe programming operation less than a remaining portion of theprogramming operation.
 16. The method of claim 14, wherein returning toincreasing the second voltage comprises returning to increasing thesecond voltage for a third plurality of steps of the programmingoperation.
 17. The method of claim 9, wherein the particular point isdetermined by a criterion selected from a group consisting of a numberof programming cycles having been reached, completion of programming fora particular programming level, a shift from a CS2 pattern dominating toa CS0 pattern dominating, reaching a determined threshold voltage formemory cells of the selected access line being programmed, and reachinga particular number of steps of the first plurality of steps.
 18. Amethod of programming a memory, comprising: applying a programmingvoltage on an access line selected for a programming operation of asingle page of the memory, the selected access line having a memory cellselected for the programming operation; applying a second voltage on anaccess line unselected for the programming operation, the unselectedaccess line having a memory cell unselected for the programmingoperation, wherein the selected memory cell and the unselected memorycell are connected in series; developing a boosted channel voltage ofthe selected memory cell and the unselected memory cell while applyingthe programming voltage and applying the second voltage, wherein theprogramming voltage is expected to increase a threshold voltage of theselected memory cell, and wherein the second voltage is expected toinhibit an increase of a threshold voltage of the unselected memorycell; increasing the programming voltage for a first plurality of stepsof the programming operation; and increasing the second voltage for asecond plurality of steps during a first portion of the programmingoperation, then decreasing the second voltage at a particular point ofthe programming operation after completing the second plurality of stepsand before completing the first plurality of steps.
 19. The method ofclaim 18, wherein decreasing the second voltage at the particular pointof the programming operation comprises decreasing the second voltage toan initial voltage level of the second voltage.
 20. The method of claim18, further comprising returning to increasing the second voltage for athird plurality of steps during a second portion of the programmingoperation after decreasing the second voltage at the particular point ofthe programming operation, wherein a number of steps of the secondplurality of steps plus a number of steps of the third plurality ofsteps is less than a number of steps of the first plurality of steps.